Multi-input LLC Converter for PV Panels
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Solution Overview
Problem
Conventional microinverter systems for photovoltaics require a high number of circuit components to maintain DC/AC inversion functionalities, leading to increased cost and reduced reliability, and need to accommodate a wide range of PV panel voltages while achieving high power conversion efficiency and power density.
Innovation Solution
A multi-input LLC resonant DC-DC converter topology with a single LLC resonant tank, including an inductor, capacitor, and transformer magnetizing inductance, allows for power interfacing from multiple PV panels and external batteries using bridge circuits with PWM phase shift control for independent maximum power point tracking (MPPT).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-winding transformer with separate power switches and rectifiers is used for each port in fully isolated DC-DC converters, then electrical isolation and power conversion functionality are achieved, but the converter's volume, cost, and component count increase while reliability decreases
Solution Approach 1:
The patent merges multiple input ports into a single LLC resonant tank circuit. Multiple bridge circuits interfacing to different power sources (PV panels, batteries) share common resonant components (inductor Lr, capacitor Cr, and transformer magnetizing inductance Lm), eliminating the need for separate power switches and rectifiers for each port. This consolidation reduces component count and improves reliability while maintaining electrical isolation functionality.
Solution Approach 2:
The single LLC resonant tank serves multiple functions: it handles power conversion from multiple different power sources (PV panels with varying voltages and batteries), provides electrical isolation through the transformer, and enables independent maximum power point tracking for each source. This multi-functional design replaces what would traditionally require separate dedicated circuits for each function.
2Ease of manufacture
If conventional two-stage microinverter topology with separate DC/DC converters is used for each PV panel, then DC/AC inversion functionality is maintained, but cost increases due to higher number of circuit components
Solution Approach 1:
The patent combines multiple DC/DC conversion stages into a single LLC resonant converter. Instead of having separate half-bridge converters for each PV panel, multiple bridge circuits share a common LLC resonant tank, significantly reducing the number of power switches, inductors, capacitors, and rectifiers required while maintaining the DC/AC inversion functionality.
Solution Approach 2:
The single LLC resonant tank is designed to universally accept power from multiple different sources including PV panels with varying voltage levels and external batteries. The circuit topology allows flexible interfacing with different power sources while performing power conversion and isolation in a unified structure, reducing manufacturing cost through component sharing.
3Adaptability or versatility
If DC-DC converter is designed to interface with multiple power sources using separate circuits for each source, then compatibility with various PV panel voltages is achieved, but power density decreases due to increased converter volume
Solution Approach 1:
The patent merges multiple input interfaces into a single LLC resonant tank that can accept power from multiple PV panels with different voltage levels and external batteries. The bridge circuits provide flexible interfacing while sharing common resonant components, achieving wide voltage compatibility without proportionally increasing converter volume.
Solution Approach 2:
The LLC resonant converter is designed with universal interfacing capability to handle multiple power sources with varying voltage characteristics. The single resonant tank structure provides adaptability to different PV panel voltages and battery configurations while maintaining compact size through shared components, thus preserving high power density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the number of circuit components, lowers costs, and improves system reliability by enabling efficient power conversion across a wide range of PV panel voltages with high power density and efficiency, while maintaining independent MPPT control for each PV source.
Implementation Method 1
A single LLC resonant tank coupled to both node A and node B including a first inductor (Lr) and a capacitor (Cr) configured together with a transformer comprising a secondary winding and a primary winding that provides a magnetizing inductance which provides a second inductance (Lm) for the single LLC resonant tank
Implementation Method 2
a transformer comprising a secondary winding and a primary winding that provides a magnetizing inductance which provides a second inductance (Lm) for the single LLC resonant tank
Data Source
AI summary
A multi-input power DC-DC converter includes a first and second bridge circuit for receiving power from a first and second electric power source. The first bridge circuit includes a first power switches with a first switch output node in between, and a second bridge circuit for receiving power from a second electric power source including second power switches with a second switch output node in between. At least one of the first and second electric power source is a photovoltaic (PV) panel. A single LLC resonant tank coupled to both the first and second output node is configured together with a transformer including a secondary winding and a primary winding that provides a magnetizing inductance which provides a second inductance for the single LLC resonant tank. A rectifier is coupled to the secondary winding.